U.S. patent application number 15/529341 was filed with the patent office on 2017-09-28 for uninterruptible power supply apparatus.
This patent application is currently assigned to Toshiba Mitsubishi-Electric Industrial Systems Corporation. The applicant listed for this patent is TOSHIBA MITSUBISHI-ELECTRIC INDUSTRIAL SYSTEMS CORPORATION. Invention is credited to Masaru TOYODA.
Application Number | 20170279302 15/529341 |
Document ID | / |
Family ID | 56149476 |
Filed Date | 2017-09-28 |
United States Patent
Application |
20170279302 |
Kind Code |
A1 |
TOYODA; Masaru |
September 28, 2017 |
UNINTERRUPTIBLE POWER SUPPLY APPARATUS
Abstract
An uninterruptible power supply apparatus supplies AC power from
any one of a first inverter of a first power conversion device and
a second inverter of a second power conversion device to a load,
and when this inverter has a malfunction, the uninterruptible power
supply apparatus supplies the AC power from the other inverter to
the load. When a DC voltage provided to the second inverter is
higher than a lower limit voltage, the second power conversion
device outputs an AC voltage having a sinusoidal waveform and
falling within an acceptable input voltage range of the load, and
when the DC voltage is lower than the lower limit voltage, the
second power conversion device outputs an AC voltage having
waveform distortion within a range acceptable to the load and
falling within the acceptable input voltage range of the load.
Inventors: |
TOYODA; Masaru; (Chuo-ku,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOSHIBA MITSUBISHI-ELECTRIC INDUSTRIAL SYSTEMS CORPORATION |
Tokyo |
|
JP |
|
|
Assignee: |
Toshiba Mitsubishi-Electric
Industrial Systems Corporation
Tokyo
JP
|
Family ID: |
56149476 |
Appl. No.: |
15/529341 |
Filed: |
December 25, 2014 |
PCT Filed: |
December 25, 2014 |
PCT NO: |
PCT/JP2014/084228 |
371 Date: |
May 24, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02J 9/062 20130101 |
International
Class: |
H02J 9/06 20060101
H02J009/06 |
Claims
1. An uninterruptible power supply apparatus comprising first and
second power conversion devices, the first power conversion device
including: a first converter configured to convert AC power
supplied from a first AC power source to DC power; a first inverter
configured to convert DC power to AC power; and a first controller
configured to control the first converter and the first inverter
such that an output voltage of the first power conversion device
becomes an AC voltage, when the AC power is supplied from the first
AC power source, the DC power generated by the first converter
being stored in a power storage device and supplied to the first
inverter, and when the supply of the AC power from the first AC
power source is stopped, the DC power of the power storage device
being supplied to the first inverter, the second power conversion
device including: a second converter configured to convert AC power
supplied from a second AC power source to DC power; a second
inverter configured to convert the DC power generated by the second
converter to AC power; and a second controller configured to
control at least the second inverter, of the second converter and
the second inverter, such that: (i) in a first case in which a DC
voltage provided to the second inverter is higher than a
predetermined first voltage, an output voltage of the second power
conversion device becomes an AC voltage having a sinusoidal
waveform and falling within an acceptable input voltage range of a
load; and (ii) in a second case in which the DC voltage provided to
the second inverter is lower than the predetermined first voltage,
the output voltage of the second power conversion device becomes an
AC voltage having waveform distortion within a range acceptable to
the load and falling within the acceptable input voltage range of
the load, the AC power from any one of the first and second
inverters being supplied to the load, and the AC power from the
other inverter being supplied to the load when the one inverter has
a malfunction.
2. The uninterruptible power supply apparatus according to claim 1,
wherein the predetermined first voltage is a minimum voltage
required for the second power conversion device to output a lower
limit AC voltage within the acceptable input voltage range of the
load.
3. The uninterruptible power supply apparatus according to claim 1,
wherein the AC voltage having the waveform distortion has a
trapezoidal waveform.
4. The uninterruptible power supply apparatus according to claim 1,
wherein in the first case, the second controller controls the
second inverter such that the second inverter outputs a sinusoidal
AC voltage having an amplitude smaller than one half of an
amplitude of the DC voltage provided to the second inverter, and in
the second case, the second controller controls the second inverter
such that the second inverter outputs a sinusoidal AC voltage
having an amplitude greater than one half of the amplitude of the
DC voltage provided to the second inverter.
5. The uninterruptible power supply apparatus according to claim 4,
wherein the second controller decreases a switching frequency of
the second inverter in the second case to be lower than a switching
frequency of the second inverter in the first case.
6. The uninterruptible power supply apparatus according to claim 1,
wherein the second converter includes a rectifier configured to
rectify an AC voltage supplied from the second AC power source, and
the second controller controls the second inverter.
7. The uninterruptible power supply apparatus according to claim 1,
wherein the second converter includes a plurality of switching
elements configured to convert an AC voltage supplied from the
second AC power source to DC voltage, and the second controller
controls the second converter and the second inverter.
8. The uninterruptible power supply apparatus according to claim 1,
wherein the second power conversion device further includes an
electric double layer capacitor configured to store the DC power
generated by the second converter, and when the AC power from the
second AC power source is supplied, the DC power generated by the
second converter is stored in the electric double layer capacitor
and supplied to the second inverter, and when the supply of the AC
power from the second AC power source is stopped, the DC power of
the electric double layer capacitor is supplied to the second
inverter.
9. The uninterruptible power supply apparatus according to claim 1,
wherein the second controller controls the second inverter such
that a phase of the output voltage of the second power conversion
device matches with a phase of the output voltage of the first
power conversion device.
10. The uninterruptible power supply apparatus according to claim
1, wherein the AC power from the first inverter is supplied to the
load, and the AC power from the second inverter is supplied to the
load when the first inverter has a malfunction.
11. The uninterruptible power supply apparatus according to claim
10, wherein the second power conversion device further includes a
switching circuit configured to receive the AC power supplied from
the second AC power source and the AC power generated by the second
inverter, and provide the load with the AC power generated by the
second inverter when the second inverter is normal, and provide the
load with the AC power supplied from the second AC power source
when the second inverter has a malfunction.
12. The uninterruptible power supply apparatus according to claim
1, wherein the AC power from the second inverter is supplied to the
load, and the AC power from the first inverter is supplied to the
load when the second inverter has a malfunction.
13. The uninterruptible power supply apparatus according to claim
1, wherein when the AC power from the second AC power source is
supplied, the AC power from the second inverter is supplied to the
load, and when the supply of the AC power from the second AC power
source is stopped, the AC power from the first inverter is supplied
to the load.
14. The uninterruptible power supply apparatus according to claim
1, wherein a selected mode of a first mode and a second mode is
executed, the first mode being a mode in which the AC power from
the first inverter is supplied to the load, and the AC power from
the second inverter is supplied to the load when the first inverter
has a malfunction, and the second mode being a mode in which the AC
power from the second inverter is supplied to the load, and the AC
power from the first inverter is supplied to the load when the
second inverter has a malfunction or when the supply of the AC
power from the second AC power source is stopped.
15. The uninterruptible power supply apparatus according to claim
1, wherein the first controller controls the first converter and
the first inverter such that the output voltage of the first power
conversion device becomes a rated voltage having a sinusoidal
waveform.
16. The uninterruptible power supply apparatus according to claim
1, wherein the first controller controls the first converter and
the first inverter such that (i) the output voltage of the first
power conversion device becomes a rated voltage having a sinusoidal
waveform when the DC voltage provided to the first inverter is
higher than a predetermined second voltage, and (ii) the output
voltage of the first power conversion device becomes the AC voltage
having the waveform distortion within the range acceptable to the
load and falling within the acceptable input voltage range of the
load when the DC voltage provided to the first inverter is lower
than the second voltage.
17. The uninterruptible power supply apparatus according to claim
16, wherein the predetermined second voltage is a minimum voltage
required for the first power conversion device to output a lower
limit AC voltage within the acceptable input voltage range of the
load.
18. The uninterruptible power supply apparatus according to claim
1, wherein the first controller controls the first converter and
the first inverter such that (i) the output voltage of the first
power conversion device becomes the AC voltage having the
sinusoidal waveform and falling within the acceptable input voltage
range of the load when the DC voltage provided to the first
inverter is higher than a predetermined second voltage, and (ii)
the output voltage of the first power conversion device becomes the
AC voltage having the waveform distortion within the range
acceptable to the load and falling within the acceptable input
voltage range of the load when the DC voltage provided to the first
inverter is lower than the second voltage.
19. The uninterruptible power supply apparatus according to claim
18, wherein the predetermined second voltage is a minimum voltage
required for the first power conversion device to output a lower
limit AC voltage within the acceptable input voltage range of the
load.
Description
TECHNICAL FIELD
[0001] The present invention relates to an uninterruptible power
supply apparatus, and particularly to an uninterruptible power
supply apparatus that receives the AC power from first and second
AC power sources.
BACKGROUND ART
[0002] Conventionally, an uninterruptible power supply apparatus
includes a converter configured to convert AC power supplied from a
first AC power source to DC power, an inverter configured to
convert the DC power to AC power, and a switching circuit
configured to provide any one of the AC power generated by the
inverter and the AC power supplied from a second AC power source to
a load. When the AC power is being supplied from the first AC power
source, the DC power generated by the first converter is stored in
a battery and supplied to the inverter, and the AC power generated
by the inverter is supplied to the load.
[0003] In a power failure state in which the supply of the AC power
from the first AC power source is stopped, the DC power of the
battery is supplied to the inverter and the AC power generated by
the inverter is supplied to the load. When the inverter has a
malfunction, the AC power supplied from the second AC power source
is supplied to the load through the switching circuit. Therefore,
even when the power failure occurs or even when the inverter has a
malfunction, the operation of the load can be continued. Such
uninterruptible power supply apparatus is disclosed in, for
example, Japanese Patent Laying-Open No. 2010-124557 (PTD 1).
CITATION LIST
Patent Document
PTD 1: Japanese Patent Laying-Open No. 2010-124557
SUMMARY OF INVENTION
Technical Problem
[0004] In the conventional uninterruptible power supply apparatus,
an output voltage of the second AC power source is directly applied
to the load when the inverter has a malfunction. Therefore, when
the output voltage of the second AC power source increases above an
acceptable input voltage range of the load, the load may be broken.
Conversely, when the output voltage of the second AC power source
falls below the acceptable input voltage range of the load, the
operation of the load may stop.
[0005] Accordingly, a main object of the present invention is to
provide an uninterruptible power supply apparatus in which the
operation of a load can be continued even when an inverter has a
malfunction and an output voltage of an AC power source varies.
Solution to Problem
[0006] An uninterruptible power supply apparatus according to the
present invention includes first and second power conversion
devices. The first power conversion device includes: a first
converter configured to convert AC power supplied from a first AC
power source to DC power; a first inverter configured to convert DC
power to AC power; and a first controller configured to control the
first converter and the first inverter such that an output voltage
of the first power conversion device becomes an AC voltage. When
the AC power is supplied from the first AC power source, the DC
power generated by the first converter is stored in a power storage
device and supplied to the first inverter, and when the supply of
the AC power from the first AC power source is stopped, the DC
power of the power storage device is supplied to the first
inverter. The second power conversion device includes: a second
converter configured to convert AC power supplied from a second AC
power source to DC power; a second inverter configured to convert
the DC power generated by the second converter to AC power; and a
second controller configured to control at least the second
inverter, of the second converter and the second inverter, such
that: (i) in a first case in which a DC voltage provided to the
second inverter is higher than a predetermined first voltage, an
output voltage of the second power conversion device becomes an AC
voltage having a sinusoidal waveform and falling within an
acceptable input voltage range of a load; and (ii) in a second case
in which the DC voltage provided to the second inverter is lower
than the predetermined first voltage, the output voltage of the
second power conversion device becomes an AC voltage having
waveform distortion within a range acceptable to the load and
falling within the acceptable input voltage range of the load. The
AC power is supplied from any one of the first and second inverters
to the load, and the AC power is supplied from the other inverter
to the load when the one inverter has a malfunction.
Advantageous Effects of Invention
[0007] In the uninterruptible power supply apparatus according to
the present invention, in addition to the first power conversion
device including the first converter and the first inverter, the
second power conversion device including the second converter and
the second inverter and configured to output the AC voltage falling
within the acceptable input voltage range of the load is provided,
and the AC power is supplied from any one of the first and second
inverters to the load, and when this inverter has a malfunction,
the AC power is supplied from the other inverter to the load.
Therefore, even when the first or second inverter has a malfunction
and the AC voltage of the AC power source varies, the operation of
the load can be continued.
BRIEF DESCRIPTION OF DRAWINGS
[0008] FIG. 1 is a block diagram showing a configuration of an
uninterruptible power supply apparatus according to a first
embodiment of the present invention.
[0009] FIG. 2 is a circuit block diagram showing a configuration of
a power conversion device 3 shown in FIG. 1.
[0010] FIG. 3 is a circuit diagram showing a configuration of a
converter and an inverter shown in FIG. 2.
[0011] FIG. 4 is a circuit block diagram showing a configuration of
a power conversion device 4 shown in FIG. 1.
[0012] FIG. 5 is a circuit diagram showing a configuration of a
converter and an inverter shown in FIG. 4.
[0013] FIG. 6 is a time chart showing the operation of power
conversion device 4 shown in FIG. 4.
[0014] FIG. 7 is a diagram for comparing the efficiency of power
conversion device 3 and the efficiency of power conversion device 4
shown in FIG. 1.
[0015] FIG. 8 is a block diagram showing a configuration of a power
conversion device included in an uninterruptible power supply
apparatus according to a second embodiment of the present
invention.
[0016] FIG. 9 is a block diagram showing a configuration of a power
conversion device included in an uninterruptible power supply
apparatus according to a third embodiment of the present
invention.
[0017] FIG. 10 is a block diagram showing a configuration of a
power conversion device included in an uninterruptible power supply
apparatus according to a fourth embodiment of the present
invention.
[0018] FIG. 11 is a circuit diagram showing a configuration of a
converter and an inverter shown in FIG. 10.
DESCRIPTION OF EMBODIMENTS
First Embodiment
[0019] FIG. 1 is a block diagram showing a configuration of an
uninterruptible power supply apparatus 1 according to a first
embodiment of the present invention. In FIG. 1, this
uninterruptible power supply apparatus 1 includes an AC input
terminal T1, a bypass input terminal T2, a battery terminal T3, an
AC output terminal T4, an operation unit 2, and power conversion
devices 3 and 4.
[0020] AC input terminal T1 receives AC power of a commercial
frequency from a commercial AC power source 5. Bypass input
terminal T2 receives AC power of a commercial frequency from a
bypass AC power source 6. Battery terminal T3 is connected to a
battery (power storage device) 7. Instead of battery 7, a capacitor
may be connected. AC output terminal T4 is connected to a load 8.
Load 8 is driven by the AC power.
[0021] Bypass AC power source 6 may be the same as or different
from commercial AC power source 5. Herein, commercial AC power
source 5 is the same as bypass AC power source 6. Output voltages
of commercial AC power source 5 and bypass AC power source 6 may
vary (increase or decrease) even in a normal state. Load 8 is
preferably driven by a rated AC voltage having a sinusoidal
waveform with no waveform distortion. However, load 8 can also be
driven by an AC voltage having waveform distortion and falling
within an acceptable input voltage range of load 8, as long as the
AC voltage is within a range acceptable to load 8.
[0022] Operation unit 2 includes a plurality of buttons operated by
a user of uninterruptible power supply apparatus 1, an image
display unit configured to display various types of information,
and the like. When the user operates operation unit 2,
uninterruptible power supply apparatus 1 can be powered on and off,
and any one of a first mode in which power conversion device 3 is
commonly used and power conversion device 4 is kept in reserve and
a second mode in which power conversion device 4 is commonly used
and power conversion device 3 is kept in reserve can be
selected.
[0023] In the normal state in which the AC power is supplied from
commercial AC power source 5, power conversion device 3 converts
the AC power to DC power, and stores the DC power in battery 7 and
converts the DC power to AC power. In the power failure state in
which the supply of the AC power from commercial AC power source 5
is stopped, power conversion device 3 converts the DC power of
battery 7 to AC power. Even when the output voltage of commercial
AC power source 5 varies, power conversion device 3 uses the DC
power of battery 7 to output the rated AC voltage having a
sinusoidal waveform with no waveform distortion.
[0024] Power conversion device 4 converts the AC power supplied
from bypass AC power source 6 to DC power, and converts the DC
power to AC power. When the output voltage of bypass AC power
source 6 is sufficiently high, power conversion device 4 outputs
the AC voltage having a sinusoidal waveform with no waveform
distortion and falling within the acceptable input voltage range of
load 8. When the output voltage of bypass AC power source 6
decreases, power conversion device 4 outputs the AC voltage having
waveform distortion within a range acceptable to load 8 and falling
within the acceptable input voltage range of load 8. The efficiency
of power conversion device 3 is lower than the efficiency of power
conversion device 4.
[0025] Power conversion device 3 and power conversion device 4 are
connected to each other by a communication line L1, and transmit
and receive information via communication line L1. For example,
when power conversion device 3 has a malfunction, power conversion
device 3 transmits a signal indicating the malfunction to power
conversion device 4. When power conversion device 4 has a
malfunction, power conversion device 4 transmits a signal
indicating the malfunction to power conversion device 3. In other
words, power conversion device 3 monitors whether or not power
conversion device 4 is normally operating, and power conversion
device 4 monitors whether or not power conversion device 3 is
normally operating.
[0026] Next, the operation of this uninterruptible power supply
apparatus 1 will be described. In the case where the first mode is
selected using operation unit 2, the AC power is supplied from
power conversion device 3 to load 8 when power conversion device 3
is normal, and the AC power is supplied from power conversion
device 4 to load 8 when power conversion device 3 has a
malfunction. In the power failure state in which the supply of the
AC power from commercial AC power source 5 is stopped, power
conversion device 3 converts the DC power of battery 7 to AC power
and supplies the AC power to load 8.
[0027] In the case where the second mode is selected using
operation unit 2, the AC power is supplied from power conversion
device 4 to load 8 when power conversion device 4 is normal, and
the AC power is supplied from power conversion device 3 to load 8
when power conversion device 4 has a malfunction. In the power
failure state in which the supply of the AC power from bypass AC
power source 6 is stopped, power conversion device 3 converts the
DC power of battery 7 to AC power and supplies the AC power to load
8.
[0028] Therefore, even when the power failure occurs or when
commonly-used power conversion device 3 or 4 has a malfunction, the
operation of load 8 can be continued. Even when the output voltages
of AC power sources 5 and 6 vary, the operation of load 8 can be
continued. Furthermore, even when the output voltage of bypass AC
power source 6 decreases, power conversion device 4 causes the AC
voltage to have waveform distortion within the range acceptable to
load 8, and outputs the AC voltage within the acceptable input
voltage range of load 8. Therefore, even when the output voltage of
bypass AC power source 6 decreases, the operation of load 8 can be
continued.
[0029] FIG. 2 is a circuit block diagram showing a configuration of
power conversion device 3. Power conversion device 3 temporarily
converts the three-phase AC power supplied from commercial AC power
source 5 to DC power, and converts the DC power to three-phase AC
power and supplies the three-phase AC power to load 8. For
simplicity of the figures and description, FIG. 2 shows only a
circuit for one phase.
[0030] In FIG. 2, this power conversion device 3 includes
electromagnetic contactors 11, 16 and 21, fuses 12 and 15, AC
reactors 13 and 19, a converter 14, a smoothing electrolytic
capacitor 17, an inverter 18, a capacitor 20, and a controller
22.
[0031] Electromagnetic contactor 11, fuse 12 and AC reactor 13 are
serially connected between AC input terminal T1 and an input node
of converter 14. Electromagnetic contactor 11 is controlled by
controller 22, and is turned on when using power conversion device
3 and is turned off, for example, at the time of maintenance and
inspection of power conversion device 3. When an overcurrent flows,
fuse 12 blows to protect commercial AC power source 5, power
conversion device 3 and the like. An instantaneous value of an AC
input voltage VI1 appearing at a node N1 between electromagnetic
contactor 11 and fuse 12 is detected by controller 22. Based on the
detected value of AC input voltage VI1, it is determined, for
example, whether or not the AC power is being normally supplied
from commercial AC power source 5 (i.e., whether or not the power
failure occurs).
[0032] AC reactor 13 forms a low-pass filter. AC reactor 13 allows
the AC power of a commercial frequency to pass through converter 14
from commercial AC power source 5, and prevents a signal of a
switching frequency generated at converter 14 from passing through
commercial AC power source 5.
[0033] Converter 14 is a forward converter and is controlled by
controller 22. In the normal state in which the AC power is
supplied from commercial AC power source 5, converter 14 converts
the AC power to DC power and outputs the DC power to a power source
node N2. An output voltage of converter 14 can be controlled to a
desired value. In the power failure state in which the supply of
the AC power from commercial AC power source 5 is stopped, the
operation of converter 14 is stopped.
[0034] Power source node N2 is connected to battery terminal T3
with fuse 15 and electromagnetic contactor 16 interposed
therebetween. When an overcurrent flows, fuse 15 blows to protect
power conversion device 3, battery 7 and the like. Electromagnetic
contactor 16 is controlled by controller 22, and is turned on when
using power conversion device 3 and is turned off, for example, at
the time of maintenance and inspection of power conversion device 3
and battery 7. Smoothing electrolytic capacitor 17 is connected to
power source node N2 and smoothes a voltage of power source node
N2. An instantaneous value of a DC voltage VDC1 appearing at power
source node N2 is detected by controller 22.
[0035] Inverter 18 is a reverse converter and is controlled by
controller 22. Inverter 18 converts the DC power generated by
converter 14 or the DC power of battery 7 to AC power of a
commercial frequency, and outputs the AC power to an output node
18a. Namely, inverter 18 converts the DC power supplied from
converter 14 through power source node N2 to the AC power in the
normal state, and converts the DC power supplied from battery 7 to
the AC power in the power failure state. An output voltage of
inverter 18 can be controlled to a desired value.
[0036] Output node 18a of inverter 18 is connected to one terminal
of electromagnetic contactor 21 with AC reactor 19 interposed
therebetween, and the other terminal of electromagnetic contactor
21 is connected to AC output terminal T4. Capacitor 20 is connected
to one terminal of electromagnetic contactor 21. AC reactor 19 and
capacitor 20 form a low-pass filter. AC reactor 19 and capacitor 20
allow the AC power of a commercial frequency generated by inverter
18 to pass through AC output terminal T4, and prevent a signal of a
switching frequency generated at inverter 18 from passing through
AC output terminal T4.
[0037] Electromagnetic contactor 21 is controlled by controller 22,
and is turned on when using power conversion device 3 and is turned
off, for example, at the time of a malfunction of inverter 18 and
at the time of maintenance and inspection of power conversion
device 3. An instantaneous value of an AC output voltage VO
appearing at AC output terminal T4 is detected by controller
22.
[0038] Controller 22 operates based on a signal provided from
operation unit 2 and a signal provided from a controller 38 (see
FIG. 4) of power conversion device 4 via communication line L1,
detects the instantaneous values of AC input voltage VI1, DC
voltage VDC1 and AC output voltage VO, and controls the whole of
power conversion device 3 based on these detected values. Namely,
based on the detected value of AC input voltage VI1, controller 22
detects whether or not the supply of the AC power from commercial
AC power source 5 has been stopped. When the AC power is supplied
from commercial AC power source 5 in the first mode (or when power
conversion device 4 has a malfunction in the second mode),
controller 22 controls converter 14 and inverter 18 in
synchronization with a phase of AC input voltage VI1.
[0039] Controller 22 controls converter 14 such that DC voltage
VDC1 becomes a desired target DC voltage VDCT1. Controller 22
controls inverter 18 such that output voltage VO changes to a rated
voltage having a sinusoidal waveform with no waveform distortion.
Controller 22 controls inverter 18 such that a phase of output
voltage VO matches with a phase of input voltage VI1.
[0040] When the supply of the AC power from commercial AC power
source 5 is stopped in the first mode (or when power conversion
device 4 has a malfunction in the second mode), controller 22 stops
the operation of converter 14 and continues the operation of
inverter 18. When DC voltage VDC1 becomes lower than a discharge
end voltage of battery 7, controller 22 stops the operation of
inverter 18.
[0041] Furthermore, when inverter 18 has a malfunction in the first
mode, controller 22 transmits a signal indicating the malfunction
to controller 38 of power conversion device 4 via communication
line L1. When a signal indicating that an inverter 34 (see FIG. 4)
has a malfunction is transmitted from controller 38 via
communication line L1 in the second mode, controller 22 drives
inverter 18 instantaneously.
[0042] FIG. 3 is a circuit diagram showing a configuration of
converter 14 and inverter 18. In FIG. 3, converter 14 includes
input nodes 14a to 14c, switching elements S1 to S6 and diodes D1
to D6, and inverter 18 includes switching elements S11 to S16,
diodes D11 to D16 and output nodes 18a to 18c.
[0043] Input nodes 4a to 4c of converter 14 receive the three-phase
AC voltage supplied from commercial AC power source 5,
respectively. One electrodes of switching elements S1 to S3 are
connected to a DC positive bus LP1, and the other electrodes
thereof are connected to input nodes 4a to 4c, respectively. One
electrodes of switching elements S4 to S6 are connected to input
nodes 4a to 4c, respectively, and the other electrodes thereof are
connected to a DC negative bus LN1. Diodes D1 to D6 are connected
in antiparallel to switching elements S1 to S6, respectively.
Smoothing electrolytic capacitor 17 is connected between DC
positive bus LP1 and DC negative bus LN1, and smoothes DC voltage
VDC1 between buses LP1 and LN1.
[0044] One electrodes of switching elements S11 to S13 of inverter
18 are connected to DC positive bus LP1, and the other electrodes
thereof are connected to output nodes 18a to 18c, respectively. One
electrodes of switching elements S14 to S16 are connected to output
nodes 18a to 18c, respectively, and the other electrodes thereof
are connected to DC negative bus LN1. Diodes D11 to D16 are
connected in antiparallel to switching elements S11 to S16,
respectively.
[0045] Each of switching elements S1 to S6 and S11 to S16 is
controlled by controller 22 and is turned on and off at prescribed
timing in synchronization with three-phase AC voltage VI supplied
from commercial AC power source 5. Switching elements S1 to S3 are
turned on and off in synchronization with three-phase AC voltage
VI1, and when switching elements S1 to S3 are turned on/off,
switching elements S4 to S6 are turned off/on, respectively.
Switching elements S11 to S13 are turned on and off in
synchronization with three-phase AC voltage VI1, and when switching
elements S11 to S13 are turned on/off, switching elements S14 to
S16 are turned off/on, respectively.
[0046] By adjusting a phase difference between three-phase AC
voltage VI1 supplied from commercial AC power source 5 and the
timing of turning on and off switching elements S1 to S6, DC
voltage VDC1 can be adjusted to a desired voltage. In addition, by
adjusting the time of turning on each of switching elements S11 to
S16, output voltage VO can be adjusted to a desired voltage.
[0047] When converter 14 and inverter 18 are operated, controller
22 turns on/off each of switching elements S1 to S6 of converter 14
such that DC voltage VDC1 becomes prescribed target voltage VDCT1,
and turns on/off each of switching elements S11 to S16 of inverter
18 such that output voltage VO becomes the rated AC voltage having
a sinusoidal waveform with no waveform distortion. An amplitude of
output voltage VO is set to have a value smaller than
VDCT1.times.1/2. Furthermore, controller 22 turns on/off each of
switching elements S11 to S16 of inverter 18 such that the phase of
output voltage VO matches with the phase of input voltage VI1.
[0048] Now, the operation of power conversion device 3 is
described. First, description is given of a case in which the first
mode is selected using operation unit 2 and power conversion device
3 outputs the AC power to load 8. In the normal state in which the
AC power is supplied from commercial AC power source 5,
electromagnetic contactors 11, 16 and 21 are ON. The AC power
supplied from commercial AC power source 5 is converted to DC power
by converter 14. The DC power generated by converter 14 is stored
in battery 7, and is converted to AC power by inverter 18 and the
AC power is supplied to load 8.
[0049] Output voltage VO of power conversion device 3 is maintained
at the rated AC voltage having a sinusoidal waveform with no
waveform distortion. Even when the output voltage of commercial AC
power source 5 decreases temporarily, voltage VDC1 of power source
node N2 is maintained constant by battery 7 and output voltage VO
is maintained at the rated AC voltage having a sinusoidal
waveform.
[0050] In the power failure state in which the supply of the AC
power from commercial AC power source 5 is stopped, the operation
of converter 14 is stopped and the DC power of battery 7 is
supplied to inverter 18. Inverter 18 converts the DC power supplied
from battery 7 to AC power, and supplies the AC power to load 8.
Therefore, even when the power failure occurs, the operation of
load 8 can be continued during a period in which the DC power is
kept in store in battery 7.
[0051] When inverter 18 has a malfunction in the normal state,
switching elements S11 to S16 of inverter 18 are fixed in the OFF
state, and the signal indicating that inverter 18 has a malfunction
is transmitted to power conversion device 4 and the AC power is
supplied from power conversion device 4 to load 8. Since the phase
of the output voltage of power conversion device 4 is synchronized
with the phase of output voltage VO of power conversion device 3,
an overcurrent never flows when the AC power is supplied from power
conversion device 4 to load 8.
[0052] When the second mode is selected using operation unit 2, the
AC power is supplied from power conversion device 4 to load 8. When
power conversion device 4 is normal, converter 14 is operated such
that DC voltage VDC1 is maintained at target voltage VDCT, and the
operation of inverter 18 is stopped such that switching elements
S11 to S16 of inverter 18 are fixed in the OFF state.
[0053] At this time, controller 22 internally generates a control
signal for controlling switching elements S11 to S16 in
synchronization with AC voltage V11, and stands by in a state of
being capable of controlling switching elements S11 to S16
immediately when power conversion device 4 has a malfunction.
Therefore, when a notification that power conversion device 4 has a
malfunction is provided from controller 38 of power conversion
device 4, the AC power is instantaneously supplied from power
conversion device 3 to load 8.
[0054] FIG. 4 is a circuit block diagram showing a configuration of
power conversion device 4. Power conversion device 4 temporarily
converts the three-phase AC power supplied from bypass AC power
source 6 to DC power, and converts the DC power to three-phase AC
power. For simplicity of the figures and description, FIG. 4 shows
only a circuit for one phase.
[0055] In FIG. 4, this power conversion device 4 includes AC
reactors 31 and 35, a converter 32, a smoothing electrolytic
capacitor 33, inverter 34, a capacitor 36, an electromagnetic
contactor 37, and controller 38.
[0056] AC reactor 31 is connected between bypass input terminal T2
and an input node of converter 32. AC reactor 31 forms a low-pass
filter. AC reactor 31 allows the AC power of a commercial frequency
to pass through converter 32 from bypass AC power source 6, and
prevents a signal of a switching frequency generated at converter
32 from passing through bypass AC power source 6. An instantaneous
value of an AC input voltage VI2 appearing at bypass input terminal
T2 is detected by controller 38.
[0057] Converter 32 is a rectifier, and converts the AC power to DC
power and outputs the DC power to a power source node N12. An
output voltage of converter 32 changes in accordance with the
output voltage of bypass AC power source 6. Smoothing electrolytic
capacitor 33 is connected to power source node N12 and smoothes a
voltage of power source node N12. An instantaneous value of a DC
voltage VDC2 appearing at power source node N12 is detected by
controller 38.
[0058] Inverter 34 is a reverse converter and is controlled by
controller 38. Inverter 34 converts the DC power generated by
converter 32 to AC power of a commercial frequency, and outputs the
AC power to an output node 34a. An output voltage of inverter 34
can be controlled to a desired value.
[0059] Output node 34a of inverter 34 is connected to one terminal
of electromagnetic contactor 37 with AC reactor 35 interposed
therebetween, and the other terminal of electromagnetic contactor
37 is connected to AC output terminal T4. Capacitor 36 is connected
to one terminal of electromagnetic contactor 37. AC reactor 35 and
capacitor 36 form a low-pass filter. AC reactor 35 and capacitor 36
allow the AC power of a commercial frequency generated by inverter
34 to pass through AC output terminal T4, and prevent a signal of a
switching frequency generated at inverter 34 from passing through
AC output terminal T4.
[0060] Electromagnetic contactor 37 is turned on when using power
conversion device 4 and is turned off, for example, at the time of
a malfunction of inverter 34 and at the time of maintenance and
inspection of power conversion device 4. An instantaneous value of
AC output voltage VO appearing at AC output terminal T4 is detected
by controller 38.
[0061] Controller 38 operates based on a signal provided from
operation unit 2 and a signal provided from a controller 22 of
power conversion device 3 via communication line L1, detects the
instantaneous values of AC input voltage V12, DC voltage VDC2 and
AC output voltage VO, and controls the whole of power conversion
device 4 based on these detected values.
[0062] Namely, based on the detected value of AC input voltage V12,
controller 38 detects whether or not the supply of the AC power
from bypass AC power source 6 has been stopped. When the AC power
is supplied from bypass AC power source 6 in the second mode (or
when power conversion device 3 has a malfunction in the first
mode), controller 38 controls inverter 34 in synchronization with a
phase of AC input voltage V12. At this time, controller 38 controls
inverter 34 such that the phase of output voltage VO matches with
the phase of input voltage V12. Herein, commercial AC power source
5 is the same as bypass AC power source 6, and thus, the phase of
output voltage VO of power conversion device 4 matches with the
phase of output voltage VO of power conversion device 3.
[0063] When DC voltage VDC2 of power source node N12 is higher than
a predetermined lower limit voltage VL, controller 38 controls
inverter 34 such that AC voltage VO having a sinusoidal waveform
with no waveform distortion and falling within the acceptable input
voltage range of load 8 is output. When DC voltage VDC2 of power
source node N12 is lower than predetermined lower limit voltage VL,
controller 38 controls inverter 34 such that AC voltage VO having
waveform distortion within a range acceptable to load 8 and falling
within the acceptable input voltage range of load 8 is output.
Lower limit voltage VL is a minimum DC voltage required for power
conversion device 4 to output lower limit AC voltage VO within the
acceptable input voltage range of load 8.
[0064] Furthermore, when the supply of the AC power from bypass AC
power source 6 is stopped in the second mode, controller 38
transmits a signal indicating the stop to controller 22 of power
conversion device 3 via communication line L1. When inverter 34 has
a malfunction in the second mode, controller 38 transmits a signal
indicating the malfunction to controller 22 of power conversion
device 3 via communication line L1. When a signal indicating that
inverter 18 has a malfunction is transmitted from controller 22 via
communication line L1 in the first mode, controller 22 drives
inverter 34 instantaneously.
[0065] FIG. 5 is a circuit diagram showing a configuration of
converter 32 and inverter 34. In FIG. 5, converter 32 includes
input nodes 32a to 32c and diodes D21 to D26, and inverter 34
includes switching elements S31 to S36, diodes D31 to D36 and
output nodes 34a to 34c.
[0066] Input nodes 32a to 32c of converter 32 receive the
three-phase AC voltage supplied from bypass AC power source 6,
respectively. Anodes of diodes D21 to D23 are connected to input
nodes 32a to 32c, respectively, and cathodes thereof are connected
to a DC positive bus LP2. Anodes of diodes D24 to D26 are connected
to a DC negative bus LN2, and cathodes thereof are connected to
input nodes 32a to 32c, respectively. The three-phase AC voltage
supplied from bypass AC power source 6 is subjected to full-wave
rectification by diodes D21 to D26 and is converted to DC voltage
VDC2. Smoothing electrolytic capacitor 33 is connected between DC
positive bus LP2 and DC negative bus LN2, and smoothes DC voltage
VDC2 between buses LP2 and LN2.
[0067] One electrodes of switching elements S31 to S33 of inverter
34 are connected to DC positive bus LP2, and the other electrodes
thereof are connected to output nodes 34a to 34c, respectively. One
electrodes of switching elements S34 to S36 are connected to output
nodes 34a to 34c, respectively, and the other electrodes thereof
are connected to DC negative bus LN2. Diodes D31 to D36 are
connected in antiparallel to switching elements S31 to S36,
respectively.
[0068] Each of switching elements S31 to S36 is controlled by
controller 38 and is turned on and off at prescribed timing in
synchronization with three-phase AC voltage VI2 supplied from
bypass AC power source 6. Switching elements S31 to S33 are turned
on and off in synchronization with three-phase AC voltage VI2, and
when switching elements S31 to S33 are turned on/off, switching
elements S34 to S36 are turned off/on, respectively. By adjusting
the time of turning on each of switching elements S31 to S36,
output voltage VO can be adjusted to a desired voltage.
[0069] When inverter 34 is operated, controller 38 turns on/off
each of switching elements S31 to S36 such that the phase of output
voltage VO matches with the phase of input voltage VI2. When DC
voltage VDC2 of power source node N12 is higher than lower limit
voltage VL, controller 38 turns on/off each of switching elements
S31 to S36 such that AC voltage VO having a sinusoidal waveform
with no waveform distortion and falling within the acceptable input
voltage range of load 8 is output.
[0070] Furthermore, when DC voltage VDC2 of power source node N12
is lower than lower limit voltage VL, controller 38 turns on/off
each of switching elements S31 to S36 such that AC voltage VO
having waveform distortion within a range acceptable to load 8 and
falling within the acceptable input voltage range of load 8 is
output.
[0071] FIGS. 6(a) and 6(b) are time charts showing a waveform of
output voltage VO of power conversion device 4. FIG. 6(a) shows a
waveform of output voltage VO when DC voltage VDC2 is higher than
lower limit voltage VL, and FIG. 6(b) shows a waveform of output
voltage VO when DC voltage VDC2 is lower than lower limit voltage
VL.
[0072] As shown in FIG. 6(a), when VDC2>VL, DC voltage VDC2 is a
voltage 2.times.V1 corresponding to input voltage VI2. Controller
38 controls inverter 34 such that inverter 34 outputs sinusoidal AC
voltage VO having an amplitude of a prescribed value A1 smaller
than V1. Output voltage VO is maintained at a voltage within the
acceptable input voltage range of load 8. In this case, DC voltage
V1 is greater than amplitude A1 of AC voltage VO, and thus, output
voltage VO has a sinusoidal waveform with no distortion.
[0073] As shown in FIG. 6(b), when VDC2<VL, DC voltage VDC2 is a
voltage 2.times.V2 corresponding to input voltage V12. V2 is
smaller than V1 (V2<V1). In this case, if controller 38 controls
inverter 34 such that inverter 34 outputs sinusoidal AC voltage VO
having an amplitude of a prescribed value smaller than V2, output
voltage VO falls below the lower limit value of the acceptable
input voltage range of load 8.
[0074] Thus, controller 38 controls inverter 34 such that inverter
34 outputs sinusoidal AC voltage VO having an amplitude of a
prescribed value A2 greater than V2. In this case, DC voltage V2 is
smaller than amplitude A2 of AC voltage VO, and thus, output
voltage VO is limited within the range of -V2 to +V2 and output
voltage VO has a trapezoidal waveform, not a sinusoidal waveform.
Assuming that the amplitude is the same, a voltage value (effective
value) of the AC voltage having a trapezoidal waveform is greater
than a voltage value of the AC voltage having a sinusoidal
waveform. Therefore, output voltage VO can be maintained at the
voltage within the acceptable input voltage range of load 8.
[0075] FIG. 7 is a diagram for comparing efficiency 11 (%) of power
conversion device 3 and efficiency .eta. (%) of power conversion
device 4. The horizontal axis in FIG. 7 represents a percentage
PL/PR (%) of a load capacity PL with respect to a rated capacity PR
of each of power conversion devices 3 and 4, and the vertical axis
in FIG. 7 represents efficiency .eta. (%) of power conversion
devices 3 and 4. Efficiency .eta. corresponds to a percentage PO/PI
(%) of AC power PO supplied to load 8 with respect to AC power PI
supplied from AC power sources 5 and 6. Curves C1 and C2 represent
efficiency .eta. of power conversion devices 3 and 4, respectively.
In power conversion device 3, when PL/PR was set at 20%, 40%, 60%,
80%, and 100%, efficiency exhibited 94.5%, 96.4%, 96.8%, 96.9%, and
96.8%, respectively.
[0076] In contrast, in power conversion device 4, when PL/PR was
set at 20%, 40%, 60%, 80%, and 100%, efficiency .eta. exhibited
94.4%, 96.5%, 97.0%, 97.1%, and 97.1%, respectively. That is to
say, in the normal range of use in which PL/PR is 40 to 100%,
efficiency .eta. of power conversion device 4 was higher than
efficiency .eta. of power conversion device 3. This is because a
switching loss and a conduction loss occur in switching elements S1
to S6 of converter 14 in power conversion device 3, whereas no
switching element is included in converter 32 in power conversion
device 4.
[0077] Next, the operation of the uninterruptible power supply
apparatus shown in FIGS. 1 to 7 will be described. In an initial
state, power conversion devices 3 and 4 are normal and the AC power
is supplied from each of commercial AC power source 5 and bypass AC
power source 6. First, description is given of a case in which the
user operates operation unit 2 to select the first mode.
[0078] In this case, in power conversion device 3, the AC power
supplied from commercial AC power source 5 is converted to DC
power, and the DC power is stored in battery 7, and is converted to
AC power and the AC power is supplied to load 8. Output voltage VO
of power conversion device 3 becomes an AC voltage having a
sinusoidal waveform with no waveform distortion and is maintained
at a constant rated voltage.
[0079] Even when output voltage VI1 of commercial AC power source 5
decreases temporarily, DC voltage VDC1 of power source node N2 is
maintained constant by battery 7, and thus, output voltage VO of
power conversion device 3 is maintained at a constant rated
voltage. Load 8 is driven by the AC power supplied from power
conversion device 3.
[0080] When the supply of the AC power from commercial AC power
source 5 is stopped, i.e., when a power failure occurs, while load
8 is being driven by power conversion device 3, the operation of
converter 14 is stopped, and the DC power of battery 7 is converted
to AC power by inverter 18 and the AC power is supplied to load 8
in power conversion device 3. Therefore, even when the power
failure occurs, the operation of load 8 can be continued during a
period in which the DC power is kept in store in battery 7.
[0081] When inverter 18 has a malfunction while load 8 is being
driven by power conversion device 3, inverter 34 of power
conversion device 4 operates instantaneously and the AC power
generated at power conversion device 4 is supplied to load 8 and
the operation of load 8 is continued. Furthermore, electromagnetic
contactor 21 is turned off to electrically separate inverter 18
from AC output terminal T4.
[0082] In power conversion device 4, the AC power supplied from
bypass AC power source 6 is converted to DC power, and the DC power
is converted to AC power and the AC power is supplied to load 8.
When output voltage V12 of bypass AC power source 6 is sufficiently
high, VDC2>VL is achieved, and output voltage VO of power
conversion device 4 becomes an AC voltage having a sinusoidal
waveform with no waveform distortion and is maintained at a voltage
within the acceptable input voltage range of load 8.
[0083] When output voltage VI2 of bypass AC power source 6
decreases and VDC2<VL is achieved, output voltage VO of power
conversion device 4 becomes an AC voltage having waveform
distortion within a range acceptable to load 8 and is maintained at
a voltage within the acceptable input voltage range of load 8.
[0084] Next, description will be given of a case in which the user
operates operation unit 2 to select the second mode. In this case,
in power conversion device 4, the AC power supplied from bypass AC
power source 6 is converted to DC power, and the DC power is
converted to AC power and the AC power is supplied to load 8. When
output voltage VI2 of bypass AC power source 6 is sufficiently
high, VDC2>VL is achieved and AC voltage VO having a sinusoidal
waveform with no waveform distortion and falling within the
acceptable input voltage range of load 8 is supplied to load 8.
When output voltage V12 of bypass AC power source 6 decreases and
VDC2<VL is achieved, AC voltage VO having waveform distortion
within a range acceptable to load 8 and falling within the
acceptable input voltage range of load 8 is supplied to load 8.
[0085] When the supply of the AC power from bypass AC power source
6 is stopped, i.e., when a power failure occurs, while load 8 is
being driven by power conversion device 4, the operation of
converter 14 is stopped, and the DC power of battery 7 is converted
to AC power by inverter 18 and the AC power is supplied to load 8
in power conversion device 3. Therefore, even when the power
failure occurs, the operation of load 8 can be continued during a
period in which the DC power is kept in store in battery 7. Output
voltage VO of power conversion device 3 becomes an AC voltage
having a sinusoidal waveform with no waveform distortion and is
maintained at a constant rated voltage.
[0086] When inverter 34 has a malfunction while load 8 is being
driven by power conversion device 4, inverter 18 of power
conversion device 3 operates instantaneously and the AC power
generated at power conversion device 3 is supplied to load 8 and
the operation of load 8 is continued. Furthermore, electromagnetic
contactor 37 is turned off to electrically separate inverter 34
from AC output terminal T4. Output voltage VO of power conversion
device 3 becomes an AC voltage having a sinusoidal waveform with no
waveform distortion and is maintained at a constant rated
voltage.
[0087] Even when output voltage VU of commercial AC power source 5
decreases temporarily, DC voltage VDC1 of power source node N2 is
maintained constant by battery 7 and output voltage VO of power
conversion device 3 is maintained at a constant rated voltage. Load
8 is driven by the AC power supplied from power conversion device
3.
[0088] When the supply of the AC power from commercial AC power
source 5 is stopped, i.e., when a power failure occurs, while load
8 is being driven by power conversion device 3, the operation of
converter 14 is stopped, and the DC power of battery 7 is converted
to AC power by inverter 18 and the AC power is supplied to load 8
in power conversion device 3. Therefore, even when the power
failure occurs, the operation of load 8 can be continued during a
period in which the DC power is kept in store in battery 7.
[0089] As described above, in this first embodiment, power
conversion device 3 configured to convert the output voltage of
commercial AC power source 5 to a rated voltage having a sinusoidal
waveform, and power conversion device 4 configured to convert the
output voltage of bypass AC power source 6 to a voltage falling
within the acceptable input voltage range of load 8 are provided,
and the AC power is supplied from any one of power conversion
devices 3 and 4 to load 8, and when this power conversion device
has a malfunction, the AC power is supplied from the other power
conversion device to load 8. Therefore, even when the output
voltages of AC power sources 5 and 6 vary and any one of power
conversion devices 3 and 4 has a malfunction, the operation of load
8 can be continued.
[0090] Furthermore, even when DC voltage VDC2 generated at
converter 32 falls below lower limit voltage VL, power conversion
device 4 causes the AC voltage to have waveform distortion within a
range acceptable to load 8 and outputs AC voltage VO falling within
the acceptable input voltage range of load 8. Therefore, even when
the output voltage of bypass AC power source 6 decreases, the
operation of load 8 can be continued.
[0091] Furthermore, of the first mode in which power conversion
device 3 is commonly used and power conversion device 4 is used
when power conversion device 3 has a malfunction, and the second
mode in which power conversion device 4 is commonly used and power
conversion device 3 is used when power conversion device 4 has a
malfunction, the selected mode is executed. Therefore, the quality
of the AC power supplied to load 8 can be changed in accordance
with the specifications of load 8.
[0092] Furthermore, the rectifier including six diodes D21 to D26
is used as converter 32, and thus, the power loss in converter 32
can be suppressed.
[0093] When DC voltage VDC2 falls below lower limit voltage VL, the
switching frequency for turning on and off switching elements S31
to S36 of inverter 34 may be further reduced to cause output
voltage VO of power conversion device 4 to have waveform
distortion. In this case, the number of times of turning on and off
switching elements S31 to S36 of inverter 34 is reduced, and thus,
the switching loss in switching elements S31 to S36 can be reduced
and efficiency .eta. of power conversion device 4 can be further
increased.
[0094] Although power conversion device 3 constantly outputs rated
AC voltage VO having a sinusoidal waveform with no waveform
distortion in this first embodiment, the present invention is not
limited thereto. Similarly to power conversion device 4, when DC
voltage VDC1 of power source node N2 falls below lower limit
voltage VL, power conversion device 3 may output AC voltage VO
having waveform distortion within a range acceptable to load 8 and
falling within the acceptable input voltage range of load 8. In
this case, the operation time of load 8 at the time of a power
failure can be lengthened.
[0095] Furthermore, similarly to power conversion device 4, even
when DC voltage VDC1 of power source node N2 is higher than lower
limit voltage VL, power conversion device 3 may output AC voltage
VO having a sinusoidal waveform and falling within the acceptable
input voltage range of load 8. In this case, by reducing DC voltage
VDC1, the conduction loss and the switching loss in switching
elements S1 to S6 and S11 to S16 can be reduced.
[0096] In this first embodiment, description has been given of the
case in which the phase of the output voltage of commercial AC
power source 5 is the same as the phase of the output voltage of
bypass AC power source 6. However, the present invention is also
applicable to a case in which the phase of the output voltage of
commercial AC power source 5 is different from the phase of the
output voltage of bypass AC power source 6. In such a case,
controller 38 of power conversion device 4 needs to control
switching elements S31 to S36 of inverter 34 in synchronization
with the phase of the output voltage of commercial AC power source
5, or controller 22 of power conversion device 3 needs to control
switching elements S11 to S16 of inverter 18 in synchronization
with the phase of the output voltage of bypass AC power source 6.
As a result, even when the phases of the output voltages of AC
power sources 5 and 6 do not match with each other, the phases of
the output voltages of power conversion devices 3 and 4 can match
with each other, and an overcurrent never flows even when the
inverter of one of power conversion devices 3 and 4 has a
malfunction and the inverter of the other power conversion device
is operated.
Second Embodiment
[0097] FIG. 8 is a circuit block diagram showing a configuration of
a power conversion device 40 included in an uninterruptible power
supply apparatus according to a second embodiment of the present
invention, and is a diagram compared with FIG. 4. Referring to FIG.
8, a difference between this power conversion device 40 and power
conversion device 4 in FIG. 4 is that an electric double layer
capacitor 41 is connected to power source node N12.
[0098] In this power conversion device 40, in the normal mode in
which the AC power is supplied from bypass AC power source 6, the
AC power supplied from bypass AC power source 6 is converted to DC
power by converter 32 and the DC power is stored in electric double
layer capacitor 41 and supplied to inverter 34. In an instantaneous
stop mode in which the supply of the AC power from bypass AC power
source 6 is temporarily stopped, the DC power of electric double
layer capacitor 41 is supplied to inverter 34. Since the remaining
configuration and operation are the same as those of the first
embodiment, description thereof will not be repeated.
[0099] In this second embodiment, the same effect as that of the
first embodiment can be obtained, and even when the supply of the
AC power from bypass AC power source 6 is temporarily stopped while
load 8 is being driven by the AC power generated at power
conversion device 40, the operation of load 8 can be continued
during a period in which the DC power is kept in store in electric
double layer capacitor 41.
[0100] The DC power stored in electric double layer capacitor 41 is
smaller than the DC power stored in battery 7. Therefore, in the
second embodiment, the operation of load 8 can be continued at the
time of an instantaneous or short-time (e.g., for several seconds)
power failure of bypass AC power source 6, whereas the operation of
load 8 cannot be continued at the time of a long-time power
failure.
Third Embodiment
[0101] FIG. 9 is a circuit block diagram showing a configuration of
a power conversion device 50 included in an uninterruptible power
supply apparatus according to a third embodiment of the present
invention, and is a diagram compared with FIG. 4. Referring to FIG.
9, a difference between this power conversion device 50 and power
conversion device 4 in FIG. 4 is that electromagnetic contactors 51
and 53 and semiconductor switch 52 are added.
[0102] One terminal of electromagnetic contactor 51 is connected to
bypass input terminal T2, and the other terminal thereof is
connected to an input node of converter 32 with AC reactor 31
interposed therebetween. Electromagnetic contactor 51 is controlled
by controller 38, and is turned on when using power conversion
device 50 and is turned off, for example, at the time of
maintenance and inspection of power conversion device 50.
[0103] Semiconductor switch 52 is connected between bypass input
terminal T2 and AC output terminal T4. Semiconductor switch 52
includes a thyristor and is controlled by controller 38.
Semiconductor switch 52 is normally OFF, and when inverter 34 has a
malfunction in the second mode, semiconductor switch 52 is
instantaneously turned on and allows the AC power supplied from
bypass AC power source 6 to pass through AC output terminal T4.
Semiconductor switch 52 is turned off after a prescribed time
period elapses since semiconductor switch 52 was turned on.
[0104] Electromagnetic contactor 53 is connected in parallel to
semiconductor switch 52 and is controlled by controller 38.
Electromagnetic contactor 53 is turned off in an inverter power
feeding mode in which the AC power generated by inverter 34 is fed
to AC output terminal T4, and is turned on in a bypass power
feeding mode in which the AC power supplied from bypass AC power
source 6 is fed to AC output terminal T4. Electromagnetic contactor
37 is turned on in the inverter power feeding mode, and is turned
off in the bypass power feeding mode.
[0105] In addition, when inverter 34 has a malfunction in the
second mode, electromagnetic contactor 53 is turned on and provides
the AC power supplied from bypass AC power source 6 to AC output
terminal T4. When inverter 34 has a malfunction, electromagnetic
contactor 37 is turned off. Namely, when inverter 34 has a
malfunction, semiconductor switch 52 is instantaneously turned on
for a prescribed time period and electromagnetic contactor 53 is
turned on and electromagnetic contactor 37 is turned off. This is
done in order to prevent semiconductor switch 52 from being
overheated and broken. By operating operation unit 2, one of the
inverter power feeding mode and the bypass power feeding mode can
also be selected manually. Since the remaining configuration and
operation are the same as those of the first embodiment,
description thereof will not be repeated.
[0106] In this third embodiment, the same effect as that of the
first embodiment can be obtained, and even when inverter 34 further
has a malfunction while inverter 34 of power conversion device 4 is
supplying the AC power to load 8 after inverter 18 of power
conversion device 3 has a malfunction in the second mode, the AC
power can be supplied from bypass AC power source 6 to load 8 and
the operation of load 8 can be continued.
Fourth Embodiment
[0107] FIG. 10 is a circuit block diagram showing a configuration
of a power conversion device 55 included in an uninterruptible
power supply apparatus according to a fourth embodiment of the
present invention, and is a diagram compared with FIG. 4. Referring
to FIG. 10, a difference between this power conversion device 55
and power conversion device 4 in FIG. 4 is that converter 32 and
controller 38 are replaced with a converter 56 and a controller 57,
respectively.
[0108] Controller 57 controls converter 56 in synchronization with
input voltage VI2 (output voltage of bypass AC power source 6).
Converter 56 is controlled by controller 57, and converts the AC
power supplied from bypass AC power source 6 to DC power and
outputs the DC power to power source node N12. Converter 56 outputs
DC voltage VDC2 having an amplitude corresponding to an amplitude
of input voltage VI2.
[0109] FIG. 11 is a circuit diagram showing a configuration of
converter 56 and inverter 34, and is a diagram compared with FIG.
5. The configuration of inverter 34 is as shown in FIG. 5.
Converter 56 includes input nodes 56a to 56c, switching elements
S21 to S26 and diodes D21 to D26.
[0110] Input nodes 56a to 56c of converter 56 receive the
three-phase AC voltage from bypass AC power source 6, respectively.
One electrodes of switching elements S21 to S23 are connected to DC
positive bus LP2, and the other electrodes thereof are connected to
input nodes 37a to 37c, respectively. One electrodes of switching
elements S24 to S26 are connected to input nodes 37a to 37c,
respectively, and the other electrodes thereof are connected to DC
negative bus LN2. Diodes D21 to D26 are connected in antiparallel
to switching elements S21 to S26, respectively. Smoothing
electrolytic capacitor 33 is connected between DC positive bus LP2
and DC negative bus LN2, and smoothes DC voltage VDC2 between buses
LP2 and LN2.
[0111] Each of switching elements S21 to S26 is controlled by
controller 57 and is turned on and off at prescribed timing in
synchronization with three-phase AC voltage VI2 supplied from
bypass AC power source 6. Switching elements S21 to S23 are turned
on and off in synchronization with three-phase AC voltage VI2, and
when switching elements S21 to S23 are turned on/off, switching
elements S24 to S26 are turned off/on, respectively. As a result,
DC voltage VDC2 having an amplitude corresponding to an amplitude
of AC voltage VI2 is generated.
[0112] This output voltage VDC2 of converter 56 is higher than
output voltage VDC2 of converter 32 in FIG. 5 by two times of the
forward drop voltage of diode D. Therefore, the lower limit value
of input voltage VI2 (output voltage of bypass AC power source 6)
that can drive load 8 can be reduced by that amount. Since the
remaining configuration and operation are the same as those of the
first embodiment, description thereof will not be repeated.
[0113] In this fourth embodiment, the same effect as that of the
first embodiment can be obtained and the lower limit value of input
voltage VI2 (output voltage of bypass AC power source 6) that can
drive load 8 can be reduced.
[0114] Although output voltage VDC2 of converter 56 is changed in
accordance with the level of the amplitude of input voltage VI2 in
this fourth embodiment, the present invention is not limited
thereto. Output voltage VDC2 of converter 56 may be maintained at a
certain value when input voltage VI2 is higher than a prescribed
value, and output voltage VDC2 of converter 56 may be set at a
greatest possible value when input voltage VI is lower than the
prescribed value. By adjusting a difference between the phase of AC
voltage VI2 and the phase of the timing of turning on and off
switching elements S21 to S26, output voltage VDC2 of converter 56
can be adjusted to a desired value.
[0115] It should be understood that the embodiments disclosed
herein are illustrative and non-restrictive in every respect. The
scope of the present invention is defined by the terms of the
claims, not the description above, and is intended to include any
modifications within the meaning and scope equivalent to the terms
of the claims.
REFERENCE SIGNS LIST
[0116] 1 uninterruptible power supply apparatus; 2 operation unit;
3, 4, 40, 50, 55 power conversion device; L1 communication line; 5
commercial AC power source; 6 bypass AC power source; 7 battery; 8
load; T1 AC input terminal; T2 bypass input terminal; T3 battery
terminal; T4 AC output terminal; 11, 16, 21, 37, 51, 53
electromagnetic contactor; 12, 15 fuse; 13, 19, 31, 35 AC reactor;
14, 32, 56 converter; 17, 33 smoothing electrolytic capacitor; 18,
34 inverter; 20, 36 capacitor; 22, 38, 57 controller; S1 to S6, S11
to S16, S21 to S26, S31 to S36 switching element; D1 to D6, D11 to
D16, D21 to D26, D31 to D36 diode; 41 electric double layer
capacitor; 52 semiconductor switch.
* * * * *